The present invention relates generally to carbon nanotubes and more particularly to direct growth of carbon nanotubes on a metal surface.
Carbon nanotubes have captured the attention of materials scientists and technologists due to their unique one-dimensional structure by virtue of which they acquire superior electrical, mechanical and chemical properties. For example, due to their high current carrying capacity (about 1010 Amp/cm2) they are envisioned as key interconnect components of future nanoelectronic devices. Though vertically aligned carbon nanotube growth on SiO2 substrates and their surface selective growth mechanism has been reported extensively in recent years, carbon nanotubes could not be directly grown on metallic substrates from the vapor phase without providing catalyst islands on the substrate. This posses a major limitation on various nanotube based applications, such as for example, use as active elements in field emission displays, sensors and other electronic devices.
Articles describe aligned nanotube growth on porous Indium Tin Oxide (ITO) coated silicon (Si) substrate (where the growth is on Si and not on ITO) and the multi-step post-production process of using carbon nanotube transfer technology enabled by open-ended carbon nanotube mats on solder material. See S. Agrawal, et al., Adv. Funct. Mat. 15, 1922 (2005) and L. Zu, et al., Nano Lett., 6, 243 (2006). These methods result in carbon nanotubes grown on silicon or ITO, or in carbon nanotubes that are indirectly attached to a substrate with a solder adhesive. However these are complicated and multi-step processes and nanotubes grown on indium tin oxide (ITO) substrates have disadvantages due to the brittle and fragile nature of ITO. To break this substrate limitation for nanotube growth, it is important to either develop new processes which will render direct growth of aligned carbon nanotubes on metals or identify suitable metals/metal alloys on which nanotubes can be grown easily with the available technologies at hand.